Luna Graphics
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Various space graphics I've made.
Anyone who wants to use these is welcome to do so.
If you use them, attribution and a link would be appreciated.
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Those who argue against using
lunar propellent imagine a ship stopping at the moon to get propellent
and then leaving for Mars. They correctly point out leaving from LEO is
easier.
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But it wouldn't be necessary to go to the moon to get lunar propellent.
Lunar propellent is much closer to LEO and EML1 than the earth. EML1
has about a 2.4 km/sec delta V advantage over LEO.

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There have been a number of recent developments regarding lunar water.
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1) Chandrayaan-1 detected hydroxyl ions in lunar regolith
in latitudes both low and high. This corroborated earlier probe data.
The earlier water findings had been dismissed as anomalies.
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2) The LCROSS impact ejecta was 5.5% water as well as 6% nitrogen, 5.7% carbon monoxide
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3) Geologist Francis McCubbins re-examined lunar samples and found
lunar magma to be 100 times more water rich than previously thought.
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4) Chandrayaan-1 and LRO radar detect elevated CPR in lunar craters.
The elevated CPR indicatessheets of relatively pure water ice, at least two meters thick,600 million tonnes at the Lunar north pole.-
These 4 developments are all very interesting. But it is sad that
development 4) is being confused with the other three. Someone might
say "Did you hear about the huge amounts of moon water they discovered"
only to get replies like "Sure. McCubbins thinks there's 16 parts per
billion water. Interesting, but not useful for a lunar base." or "A few
hydroxyl ions in the lunar regolith? So what, you'd need to mine a
mountain of dirt for a few gallons."
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In terms for usefulness to a lunar base, the elevated cpr is in a whole
other league than the earlier water findings. Once again, they indicatesheets of relatively pure water ice, at least two meters thick,600 million tonnes at the Lunar north pole.

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In terms of Delta V, EML1 is very close to LEO, GEO and lunar volatiles.

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EML1 is only 1.2
kilometers/second from grazing Mars' atmosphere. From there the
remaining velocity changed needed can be accomplished with aerobraking.

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In terms of delta-V, EML1 is
only 2.5 km/sec from the moon and 3.8 km/sec from LEO. If aerobraking
drag passes are used, it would only take .7 km/sec to get from EML1 to
LEO (red lines indicate one-way delta-V saving aerobraking paths)

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It takes about .65 km/sec to drop from EML1 to a 300 km altitude perigee.
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At perigee the cargo is moving nearly escape speed, 3.1 km/sec faster than a circular orbit at that altitude.
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3.1 - .65 is about 2.4. EML1 has about a 2.4 km/sec advantage over LEO.
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From a high apogee, plane changes are inexpensive. So it's easier to
pick your inclinitation from EML1. EML1 moves 360 degrees about the
earth each month, so you can choose your longitude of perigee when a
launch window occurs.
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This 2.4 km/sec advantage not only applies to trans Mars insertions,
but any beyond earth orbit destination (near earth asteroids, Venus,
Ceres, etc.)

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The blue line is a Phobos tether
extending both Marsward and away from Mars. The red paths are orbits
payloads would follow if released from certain points on the tether.
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This shows a Phobos tether extending 5680 kilometers to within 300
kilometers of Mars' surface. At this altitude, the tether foot is
moving about .6 km/sec with regard to Mars' surface.
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Typical chemical rocket propellent has two components: oxidizer and
fuel. While the moon has been known to be rich in oxygen, until
recently it was thought to be hydrogen poor. Fuel is usually hydrogen
or hydrogen rich compounds like methane or kerosene.
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Back when I believed lunar hydrogen was extremely rare, I was hoping
Deimos and Phobos might be fuel sources. These Martian moons are two of
the closest objects to earth in terms of delta V and there's some
suggestion they may have hydrogen rich volatiles. But since then Chandrayan 1 and LRO
have found what seems to be at least two meter thick sheets of ice in
the moon's polar craters. So the moon is a possible source of both
oxidizer and fuel.
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Even though my daydreams no longer rely on fuel from Deimos and Phobos,
these moons remain interesting to me. Phobos' high angular velocity
(about two pi radians each 7 hours and 40 minutes) and location deep in
Mars gravity well make it a good object to anchor a tether to. I
believe Phobos and Deimos will be key pieces of real estate in the
development of Mars as well as other parts of the solar system.

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I imagine 3 types of vehicles for space development.
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The yellow vehicles have a nearly 10 km/sec delta-V budget and a thick
atmosphere to contend with. It is possible these will always be
multi-stage expendable vehicles.
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The red vehicles move between locations in different orbits. They need
no landing mechanism, no thermal protection or ablation shields,
parachutes, etc. They have delta V budgets between 4 and 3 km/sec. It
is my belief such vehicles could be single stage, reusable vehicles.
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The green vehicles (lander/ascent vehicles) move between orbital
locations and a surface of a substantial body, but not as substantial
as earth. Their delta V budget is around 5 km/sec. I believe these
vehicles could also be single stage, reusable vehicles.
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It would take some investment to build infrastructure to maintain and
supply the propellent depots pictured here. Wouldn't it be cheaper to
just send ships directly from Earth to Mars? That depends. If your goal
is flags and footprints sortie missions, disposable mega rockets are
the way to go. But if you wanted genuine development of Mars, it would
take many, many trips. If infrastructure could enable these trips to be
done with smaller, reusable vehicles, the infrastructure would return
the investment many times over.

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Several types of conic sections.
Objects in two body systems (e.g. planet and moon, or star and planet)
will follow one of these types of paths.
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This is a low res version of a page from an orbital mechanics coloring book I'm working on.

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Above an ellipse is drawn trom a string tacked to each focus of the ellipse.
-Below, an asteroid follows an elliptical path about the sun with the sun at a focus. This is Kepler's 1st law.
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A body's closest point to the sun is call the perihelion, the furthest, aphelion.
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This is also a low res coloring page from an orbital mechanics coloring book.

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In a solar system without
propellent depots, travel between destinations is expensive and
wasteful, to say the least. But disposable mega rockets aren't the only
way.
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With propellent depots, we could travel between earth orbit and Mars orbit with smaller, reusable vehicles.

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The Earth, Moon, and 5 Lagrange points suggest a cosmic peace sign.
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EML1 and 2 (just above and below the moon) could be valuable as
transportation hubs in cislunar space. They could also be valuable
staging points to launch interplanetary ships from.